BONE MARROW TRANSPLANTATION
Bone marrow is the soft, spongy tissue found inside bones. It contains specialist stem cells, which produce the body’s blood cells. Stem cells in bone marrow produce three important types of blood cells. These are the stem cells needed in BMT.
- Red blood cells – which carry oxygen around the body
- White blood cells – which help fight infection.
- Platelets – which help stop bleeding/aid clotting.
A BMT, also called a stem cell transplant, is a special therapy for patients with certain cancers or other diseases. It involves transfusing healthy stem cells into the patient’s body to replace damaged or diseased bone marrow. A BMT may be necessary if the bone marrow stops working and doesn’t produce enough healthy stem cells.
There are different types of BMT depending on who the donor is:
- Autologous BMT – done using cells from the patient’s own body.
- Allogeneic BMT – done using cells from a donor, who shares the same genetic type as the patient, usually a brother or sister.
- Umbilical cord blood transplant – done using stem cells taken from an umbilical cord immediately after delivery of an infant. This has an advantage in that these stem cells reproduce into mature, functioning blood cells faster and more effectively than stem cells taken from the bone marrow of a donor.
Stem cells are tested, typed, counted, and frozen until they are needed for a transplant. BMT has been used successfully to treat diseases such as leukemias, lymphomas, aplastic anemia, immune deficiency disorders, and some solid tumor cancers.
Reasons for BMT procedure
A BMT is needed to:
- Replace diseased, damaged or non-functioning bone marrow with healthy functioning bone marrow (for conditions such as leukemia, aplastic anemia, and sickle cell anemia).
- Renew an immune system to fight leukemia or other cancers not cured by the chemotherapy or radiation used in the transplant.
- Sometimes, high and repeated doses of chemotherapy or radiation are needed to cure diseases, such as lymphoma and neuroblastoma, which can permanently damage or destroy the patient’s bone marrow stem cells. A BMT then helps replace the patient’s bone marrow and restore its normal function.
- Replace bone marrow with genetically healthy functioning bone marrow to prevent further damage from a genetic disease process (such as Hurler’s syndrome and adrenoleukodystrophy).
- The risks and benefits must be weighed in a thorough discussion with your doctor and specialists in BMTs prior to the procedure.
The following diseases are the ones that most commonly benefit from BMT:
- Severe aplastic anemia.
- Plasma cell disorders.
- Inborn errors of metabolism.
- Multiple myeloma.
- Immune deficiency disorders.
- Some solid-tumor cancers.
However, patients experience diseases differently, and BMT may not be appropriate for everyone who suffers from these diseases.
Evaluation for BMT
Matching involves typing human leukocyte antigen (HLA) tissue. The antigens on the surface of these special white blood cells determine the genetic makeup of a person’s immune system. There are at least 100 HLA antigens; however, it is believed that there are a few major antigens that determine whether a donor and recipient match. The others are considered "minor" and their effect on a successful transplant is not as well-defined.
The more the antigens match, the better the engraftment of donated marrow. Engraftment of the stem cells occurs when the donated cells make their way to the marrow and begin producing new blood cells. Most of the genes that "code" for the human immune system are on one chromosome. Since we only have two of each chromosome, one we received from each of our parents, a full sibling of a patient in need of a transplant has a one in four chance of having gotten the same set of chromosomes and being a "full match" for transplantation.
An extensive evaluation is completed by the BMT team. The decision for you to undergo a BMT will be based on many factors, including the following:
- Your age, overall health, and medical history.
- Extent of the disease.
- Availability of a donor.
- Your tolerance for specific medications, procedures, or therapies.
- Coping with the disease and the transplant.
- Your opinion or preference.
Risks of the procedure
A BMT involves several risks, some potentially fatal. The complications depend on many factors, including the type of disease or condition, the type of transplant, and the age and health of the person. Some people experience few problems with a transplant, while others may develop serious complications that may require hospitalization. The following are some complications that may occur with a BMT. However, each individual may experience symptoms differently. These complications may also occur alone, or in combination:
- Low platelets and low red blood cells.
- Pain in the form of mouth sores and gastrointestinal irritability.
- Fluid overload – Fluid overload is a complication that can lead to pneumonia, liver damage, and high blood pressure.
- Respiratory distress.
- Organ damage – The liver and heart are important organs that may be damaged during the transplantation process. Temporary or permanent damage to the liver and heart may be caused by infection, graft-versus-host disease, high doses of chemotherapy and radiation, or fluid overload.
- Graft failure – Failure of the graft (transplant) taking hold in the marrow is a potential complication.
- Graft-versus-host disease – Graft-versus-host disease (GVHD) can be a serious and life-threatening complication of a BMT. GVHD occurs when the donor’s immune system reacts against the recipient’s tissue. It typically affects yous skin, digestive tract or liver.
Before the procedure
Preparation for the recipient:
A patient who has to undergo a BMT will be:
- Assessed by the BMT team to determine whether all treatment options have been discussed and evaluated for risk versus benefit.
- Physically examined to assess overall health and status of his/her condition. This includes multiple tests to evaluate the patient’s blood and organ functions (for example, heart, kidney, liver, and lungs). The patient’s complete medical history will be checked prior to BMT.
- Asked to visit the transplant center up to 10 days prior to transplant for hydration, evaluation, placement of the central venous line, and other preparations. A catheter, also called a central venous line, will be implanted in a large vein in the chest or neck area. Blood products and medications will be administered through the catheter during treatment.
For an allogeneic transplant, finding a matching donor can be a long process, especially if a sibling match is not available. One can also look up national and international registries for registered voluntary marrow donors. A bone marrow search involves searching these registries for donors whose blood most closely resembles or matches the individual needing the transplant.
Preparation for the donor:
A healthy, matching donor is needed for carrying out a BMT. A donor can be self, sibling, parent or relative, non-related person, or umbilical cord from a related or non-related person. Some family members may be typed if a donor is not available immediately. A potential donor who matches the genetic type of the patient needing a transplant will have to undergo a series of tests related to his or her health, exposure to viruses, and genetic analysis will be done to determine the extent of the match. The donor will be given instructions on how a bone marrow donation will be made.
How are stem cells collected?
Once a match for a patient needing a BMT is found, then stem cells will be collected either from the circulating cells in the blood (the peripheral system) or from the bone marrow harvest.
- Peripheral blood stem cells. Peripheral blood stem cells (PBSCs) are collected by apheresis, a process in which the donor is connected to a special cell separation machine via a needle inserted in arm veins. Blood is taken from one vein and is circulated though the machine which removes the stem cells and returns the remaining blood and plasma back to the donor through another needle inserted into the opposite arm. Several sessions may be required to collect enough stem cells to ensure a chance of successful engraftment in the recipient. Prior to apheresis, the donor will receive daily injections of growth factor to increase stem cell production and move stem cells into his or her circulating or peripheral blood system so they can be collected.
- Bone marrow harvest. Bone marrow harvesting involves collecting stem cells with a needle placed into the soft center of the bone, the marrow. Most sites used for bone marrow harvesting are located in the hip bones and the sternum. The procedure takes place in the operating room. The donor will be anesthetized during the harvest and will not feel the needle. In recovery, the donor may experience some pain in the areas where the needle was inserted.
If the donor is the person himself or herself, previously collected and frozen stem cells, from either peripheral (apheresis) or harvest, are counted, screened, and ready to infuse.
During the procedure
The preparations for a BMT vary depending on the type of transplant, the disease requiring transplant, and your tolerance for certain medications. Consider the following: A conditioning process prepares your body for the transplant. Most often, high doses of chemotherapy and/or radiation are included in the preparations. This is done to
- Destroy cancer cells if you are being treated for a malignancy.
- Suppress your immune system.
- Prepare your bone marrow for the new stem cells.
After the chemotherapy and/or radiation is administered, the stem cell transplant can take place. On the day of your transplant, called day zero, the stem cells are given through the central venous catheter into the bloodstream. It is not a surgical procedure to place the marrow into the bone, but is similar to receiving a blood transfusion. The stem cells make their way into the bone marrow and begin reproducing and growing new, healthy blood cells. You are awake during the procedure.
During infusion of bone marrow, the patient may experience the following:
- Chest pain.
After the procedure
Once the new stem cells enter your body, they travel to your bone marrow. In time, they multiply and begin to make new, healthy blood cells. This is called engraftment. It usually takes several weeks before the number of blood cells in your body starts to return to normal. In some people, it may take longer. After the transplant, supportive care is given to prevent and treat infections, side effects of treatments, and complications. This includes frequent blood tests, close monitoring of vital signs and strict measurement of fluid input and output. You may need medicine to manage complications, such as nausea and diarrhea.
Blood counts will be checked frequently during the days following transplant to evaluate initiation and progress of engraftment. Platelets are generally the last blood cell to recover. You may need periodic transfusions of red blood cells and platelets until your bone marrow begins producing enough of those cells on its own. Engraftment can be delayed because of infection, medications, low donated stem cell count, or graft failure. Although the new bone marrow may begin making cells in the first 30 days following transplant, it may take months, even years, for the entire immune system to fully recover.
After infusion, you may:
- Spend several weeks in the hospital.
- Be susceptible to infection.
- Experience excessive bleeding.
- Be confined to a clean environment.
- Take multiple antibiotics and other medications.
- Be given medication to prevent graft-versus-host disease–if the transplant was allogeneic. The transplanted new cells (the graft) tend to attack the patient’s tissues (the host), even if the donor is a relative.
- Undergo continual laboratory testing.
- Experience nausea, vomiting, diarrhea, mouth sores, and extreme weakness.
- Experience temporary mental confusion and emotional or psychological distress.
After leaving the hospital, the recovery process continues for several months or longer, during which time the patient cannot return to work or many previously enjoyed activities. The patient must also make frequent follow-up visits to the hospital or doctor’s office. Prognosis greatly depends on the following:
- Type of transplant.
- Type and extent of the disease being treated.
- Disease response to treatment.
- Your age and overall health.
- Your tolerance of specific medications, procedures, or therapies.
- Severity of complications.
A BMT may completely or partially cure your illness. If the transplant is a success, you can go back to most of your normal activities as soon as you feel well enough. Usually it takes up to one year to recover fully